Missouri bladderpod (Physaria
filiformis)

The Missouri bladderpod is a small annual plant, about 4 to 8 inches tall, with distinctive canary-yellow flowers cluster at the top of the stems and bloom from April to May. It grows strictly in southern Missouri and northern Arkansas. It probably never grew beyond this range but was known from only nine sites in three counties when it was first listed as endangered in 1987. After more surveys and actions undertaken to conserve the bladderpod, the number of documented populations increased to 61 sites in 4 counties in Missouri and 2 sites in 2 counties in Arkansas.

Missouri bladderpods grow mostly in open limestone glades; but it has been found on one dolomite glade in Arkansas. Glades are naturally dry, treeless areas with shallow, loose soil and areas of exposed rock. Glades are described by the underlying rock (e.g., limestone or dolomite). Sometimes the bladderpod is found on highway rights-of-way and pastures where mowing and grazing have kept the area open. Occasionally it is found in open rocky woods.